ATLAS Sensitivity to the Flavour-Changing Neutral Current Decay $t \to Zq$

Abstract

The sensitivity of the ATLAS experiment to the top-quark rare decay via flavor-changing neutral currents $t \rightarrow Zq$ ($q$ represents $c$ and $u$ quarks) has been studied at $\sqrt{s}$=14 TeV in two decay modes: 1.The pure leptonic decay of gauge bosons: $t\bar{t} \rightarrow ZqWb \rightarrow l^{+} l^{-} j l^{\pm} \nu b$ , (l=e, $\mu$). 2.The leptonic decay of Z bosons and hadronic decay of W bosons: $t\bar{t} \rightarrow ZqWb \rightarrow l^{+} l^{-} jjjb$ , (l=e, $\mu$). The dominant backgrounds $Z+jets$, $WZ$ and $t\bar{t}$ have been analysed. The signal and backgrounds were generated via PYTHIA 5.7, and simulated and analysed using ATLFAST 2.14. A branching ratio for $t \rightarrow Zq$ as low as 2.0x10$^{-4}$ for the leptonic mode and 5.9x10$^{-4}$ for hadronic mode could be discovered at the 5$\sigma$ level with an integrated luminosity of 100 fb$^{-1}$.